Gas liquid detector



Dec. 21, 1965 DONALD L. MING ETAL 3,224,250

.GAS LIQUID DETECTOR Original Filed Dec. 26, 1957 4 Sheets-Sheet 1DONALD L. Ml/VG' ERNARD CASE ATTORNEY Dec. 21, 1965 DONALD L. MING ETAL3,224,250

GAS LIQUID DETECTOR Original Filed Dec. 26, 1957 4 Sheets-Sheet 2 INVENTOR. DONALD L. MING BERNARD 614$ ATTORNEY Dec. 21, 1965 DONALD L.MING ETAL 3,224,250

GAS LIQUID DETECTOR Original Filed Dec. 26, 1957 4 Sheets-Sheet 5INVENTORS DONALD L. MIA/G BERNARD CASE ATTORNEY Dec. 21, 1965 OriginalFiled Dec. 26, 1957 DONALD L. MING ETAL GAS LIQUID DETECTOR 4Sheets-Sheet 4 INVENTOR. DONALD L. M/NG BERNARD LAf A T TORN Y UnitedStates Patent Claims. or. 73-19) This invention relates to gas-liquiddetectors and has for an object to provide a gas-liquid detector whichwill quickly sense the presence of either gas or liquid in a fluid.

This is a divisional application of our co-pending application, SerialNo. 705,407, filed December 26, 1957, now abandoned.

In systems containing liquids or conduits through which liquids flow,gas is often present with the liquid; and it is sometimes desirable tosense or signal the presence of either the gas or the liquid. In somecases it is desirable that the gas be bled oif from the liquid; atypical example of such a circumstance is a rocket motor system operatedby liquid propellant. It is a common practice to supply liquidpropellant to a rocket motor through a conduit from a container of thepropellant which is pressurized by gas to force the propellant to flowinto the chamber of the rocket motor against the pressure in thatchamber. Sometimes the gas becomes entrapped with the liquid and flowsthrough the conduit toward the motor. It is generally desired to sensethe presence of the gas in the conduit before it reaches the motor andto bleed the gas off so that the fluid arrives at the motor entirelyliquid. In the case of liquid rocket motor systems a detector forsensing the condition of gas or liquid should be operable over widetemperature and pressure ranges; and also should be capable ofwithstanding corrosion or other damage when used with active propellantsuch as, for example, nitric acid.

In accordance with the present invention, we provide a sensingarrangement or system which indicates the condition of gas or liquid ina conduit or chamber; and which is well adapted for use with the liquidpropellant of rocket motors. The invention is carried out by use of avibratory reed of magnetic material arranged in the magnetic field of apair of coils. An amplifier is associated with the coils such that oneof the coils is at the amplifier output and the other of the coils atthe amplifier input. Due to the coupling between the output and inputcoils when the reed vibrates, feedback occurs between the output andinput of the amplifier which puts the amplifier in an oscillatorycondition.

A feature of the arrangement resides in placing the vibratory reed inthe fluid to be sensed, so that the reed is located either in gas orliquid depending on whether gas or liquid is present at the time. Whenthe medium around the reed is gaseous, there is little fluid viscosityand the reed vibrates freely to create the degree of feedback forsetting the amplifier to its oscillatory condition. When the mediumaround the reed is liquid the relatively higher viscosity of the liquiddamps the reed to reduce the feedback condition and oscillation does notoccur.

A suitable responsive device such as a signal at the amplifier outputcan be used to indicate the condition of oscillation or non-oscillationof the system.

In accordance with a preferred feature, a valve can be operated to bleedoff gas when the system senses the presence of gas.

The foregoing and other features will be more fully understood from thefollowing detailed description and accompanying drawings of which:

FIG. 1 shows a schematic representation of an electromechanicaloscillatory system according to this invention,

incorporated into a fluid conduit for detecting gas or liquid in thefluid conduit;

FIG. 2 is an enlarged veiw showing the details of construction of thecombination gas and liquid sensing element schematically represented inthe device of FIG. 1;

FIG. 3 is a cross section taken at line 33 in FIG. 2;

FIG. 4 is a cross section taken at line 4-4 in FIG. 3; and

FIG. 5 shows an enclosed tank for storage of fluid showing attachment ofa plurality of gas-liquid sensing elements, such as in FIGS. 1 to 4, formonitoring of the liquid or gas in the enclosed tank.

Referring to the drawings, there is shown schematically in FIG. 1 asystem according to this invention which operates as a feedbackoscillator. A sensing element 10 senses the viscosity of a fluid in itschamber 11 which is supplied from an inlet conduit 12 and discharges toan outlet conduit 13. The sensing element 10 has an electri cal inputsupplied through a pair of electrical leads represented by the lines 14and 15 which takes feedback voltage from the output of a suitableelectronic amplifier 16 represented in FIG. 1 in block diagram form. Theamplifier 16 is supplied with power from a suitable source (not shown)and with a signal from the output of the sensing element 10 through apair of electrical leads represented by the lines 17 and 18 between theamplifier 16 and a suitable phase shifting circuit means 19, representedin block diagram form. Two leads, represented by the lines 20 and 21,electrically connect the phase shifting circuit 19 to the output of thesensing element 10. A relay 22 has a coil 73 shown in phantom linesconnected by a pair of leads, represented by the lines 23 and 24, to theoutput of the amplifier 16. Output leads of the relay 22 are representedby the lines 25 and 26 and they are shown connected in series to a DC.supply 74 and relay contacts 75, both of which are shown in phantomlines.

A DC. power supply source 27 is provided for the input to the sensingelement 10 to bias its input circuit at a suitable value so that it maybe provided with a satisfactory driving power. The power supply 27 isadjustable to a suitable voltage by a rheostat 72 provided in serieswith it. Some other way may, of course, be provided to supply a suitablebias, such as bias supplied through the leads 14 and 15 from a biastaken at the output of a suitable amplifier 16. A solenoid bleed valve28 is electrically connected to the output leads 25 and 26 of the relay22. The solenoid bleed valve 28 is located in a gas bleed conduit 29which is in fluid communication with outlet conduit 13.

The electronic amplifier 16, the phase shifting circuit means 19, thefeedback connection to the amplifier by means of leads 14 and 15, therelay 22, and the solenoid bleed valve 28 are all well known electricalmeans which operate in a well-known manner and therefore need no furtherdiscussion here. The sensing element 10, shown in detail in FIGS. 2, 3and 4, comprises a case 30 of substantially non-magnetic materialpreferably of stainless steel, so as to be resistant to highly corrosivefluids and strong enough to be operable under a wide range oftemperature and pressure conditions. The inlet conduit 12 and the outletconduit 13 are suitably connected to the case 30 by couplings 31 and 32respectively, which are preferably pressure-proof and corrosion-proof inthe case of use with high pressure and corrosive fluids. The inletconduit 12 enters the interior chamber 11 through the bottom of thecase. At a side of the case near its bottom where the conduit 12 enters,the conduit 13 passes from the case. Conduit entrance 12 and conduitoutlet 13 are therefore preferably close together and are disposed withtheir centers in one place in space.

A reed 33 of magnetic material extends substantially the length of theinterior of the case. The reed is attached to the case, for example bywelding at 34, on one of its ends. The opposite end of the reed at 35 isfree and terminates in the vicinity of the conduit outlet 13. The reed33 is preferably centrally disposed with respect to the inlet conduit12. The reed has two larger sides 36 and 37, preferably flat, which aresubstantially parallel to one another.

The case 30 is provided with two exterior chambers 38 and 39 whichextend inward into the case and terminate in substantially flat endmembers, 40 and 41 respectively, which are parallel and opposite to oneanother, being separated by a space 42 only wide enough for the reed 33to vibrate freely in. The reed 33 is disposed through the space 42 withits sides 36 and 37 substantially parallel to the end members 40 and 41and preferably centrally located in the space 42. The exterior chambers38 and 39 may be of any convenient shape in cross section, a cylindricalshape being preferred for the particular embodiment shown.

In the chamber 33, a driving coil 43 is mounted on an electricalinsulation spool 44, of rubber or the like, so as to be concentricallydisposed about an imaginary cen ter line 45. The coil 43 and its spool44 are mounted in the deepest part of the chamber 38 within a mounting46, which may conveniently be a heavy rubber washer or the like. Thecore of the coil 43, within the spool, comprises a plurality oflaminated plates 47 of magnetic material which are held together byrivets 48 passed through the plates. The plates 47 are substantiallyseparated from one another, by surface oxides, varnish or the like, in acommon and well-known laminated construction so as to minimize theeffect of eddy currents generated in the core. The two ends of the wireof the coil 43 terminate at electrical terminal posts, 49 and 50respectively which are mounted on insulators 51 and 52 attached to theoutside of the case 30. The DC bias 27 and the amplifier feedback fromthe leads 14 and 15 are applied to the terminal posts 49 and 50.

The exterior chamber 39 which opposes the exterior chamber 38 holds apickup coil 53. The coil 53 is similar to the coil 43 having an axispreferably coincidental with the extended center line 45. Associatedwith coil 53 are, a spool 54, a mounting 55, a core of laminated plates56 of magnetic material having rivets 57, and two terminals 53 and 59each of which are mounted on the case 30 by insulators 60 and 61respectively. A permanent magnet 62 also is provided at an end of thecore within the end of the spool 54 which is directed toward the openend of the chamber 39. The permanent magnet 62 has its magnetic fieldoriented substantially parallel to the imaginary center line 45. Theleads 20 and 21 to the phase-shifting circuit 19 are connected to theterminals 58 and 59, so as to supply output of the pickup coil 53 to theelectronic amplifier 16.

An arrow 63 into the conduit 12 represents fluid into the chamber 11,and an arrow 64 out of the conduit 13 represents fluid out of thechamber 11. An arrow 65, as shown in FIG. 1, represents gas in the gasbleed conduit 29 which passes the solenoid bleed valve 28 when thisvalve is open. It is to be understood that the conduits, represented bydiscontinuous structure in the figures, actually extend to theiroperating parts. For example, the conduit 12 extends to a fluid supplyof liquid which may contain gas; the conduit 13 extends to fluidinjectors within the thrust chamber of rocket engine or the like; andthe gas bleed conduit extends to where ever the gas is discharged, asinto the atmosphere.

. Operation This system operates as a feedback oscillator, the vibratoryreed 33 in its fluid chamber 11 being apart of the oscillatory system.Essentially the reed 33 is incorporated into a fluid conduit system suchas the propellant conduits 12 and 13 of a rocket engine, or the like,where it distinguishes between gas and liquid because of the differencein viscosity of the gas and liquid. The relay 22 has contacts 75 whichare closed during the time the reed 33 vibrates freely in a gas mediumwithin the chamber 11, thus opening the bleed solenoid valve 28 in thegas bleed conduit 29 and permitting expulsion of gas from the propellantconduit 13 by maintaining the valve open during which time liquid fluidadvances behind the gas and expels it from the conduit through the openvalve 28. When liquid reaches the reed 33, the reed vibration issuddenly damped out and the contacts of the relay 22 open, thus causingthe solenoid bleed valve 28 to close and prevent dumping of liquidpropellant 64 through the gas bleed conduit 29.

To produce vibratory motion of the reed 33, when a gas surrounds thereed, energy is imparted to the reed by the driving coil 43 from thefeedback portion of the output of the amplifier 16 through the leads 14and 15. The resulting motion of the magnetic reed induces a voltage inthe pickup coil 53 which is fed to the phase-shifting circuit 19 whereits phase relationship is adjusted so as to be in phase with the waveenergy of the amplifier 16 so as to sustain electrical oscillation ofthe amplifier and mechanical vibratory motion of the reed. The outputvoltage of the phase-shifting circuit is thus fed to the input of theelectronic amplifier 16 in a suitable phase relationship. The reedvibration, present only when a gaseous fluid surrounds the reed 33, isself-starting by reason of the amplifier having a high amplifier gainand also due to noise voltages inherent in the electrical portion of theoscillatory system. Some slight reed vibration will occur when a liquidfluid is sensed but not enough to cause the relay coil 73 to hold thecontacts 75 open. With the contacts 75 closed, the solenoid valve 82remains open. Each of the coils 43 and 53 have magnetic coupling to thereed 33 through the members 40 and 41 respectively, of the case 30 whichis of non-magnetic material. The magnetic circuit of the pickup coilincludes the permanent magnetic 62 in addition to the laminated core ofmagnetic material. The permanent magnet 62 polarizes the pickup coil. Achange in the DC. flux in the magnetic circuit of the pickup coil isproduced by any displacement in the position of the vibratory reed whichchanges the total reluctance in this magnetic circuit, thus generating avoltage in the pickup coil.

The driving coil 43 assembly is polarized by maintaining a DC. biascurrent in it of sufficient magnitude from the DC. source 27 to providesatisfactory driving power for the particular gaseous and liquid fluidssensed by the system. For maximum driving efliciency, the reed is drivenat its natural frequency of vibration in the particular gaseous fluid,the natural frequency being dependent on physical factors such as thelength of the need, the material which it is made of, and the fluid inwhich it must vibrate. Because the quality rating or Q, of such aresonant vibratory reed is high, very little deviation in drivingfrequency can be tolerated. This problem of maintaining the properdriving frequency is solved by the feedback self-resonant systememployed in this device so that the reed 33 will always be energized at,or very near, its natural resonant frequency. For a self-resonant systemsuch as used in the present device, factors such as reed corrosion,temperature changes, introduction of foreign matter adherent to the reedsurfaces, or pressure changes, can change the resonant frequency of thereed, as in any other such system. Performance of this system is notimpaired, however, by the above factors, since the driving frequencyautomatically changes to the proper frequency in such a self-resonantsystem as this. I

This combination gas-liquid detector will automatically bleed liquidpropellant conduits of gas to ensure simultaneous arrival of liquid fueland oxidizer into rocket motor injectors. In addition, it can be used tomerely signal viscosity condition of a fluid rather than to operate asolenoid valve in response to viscosity condition of a fluid. It isoperable under wide temperature and pressure conditions, in highlycorrosive fluids such as fuming nitric acid, and in highly inflammablefluids. The device is fast acting and highly reliable.

FIG. 5 shows how one or more of the sensing ele ments and 10 of agas-liquid detector of this invention can be arranged in fluidcommunication with one another in a series manner by the conduits 76 tomonitor the liquid level in a tank 67. It is to be understood that eachof the sensing elements 10 and 10' have associated with them similarmeans of electrical circuits and electrical elements shown in FIG. 1 toto make them operable as described for FIGS. 1 to 4. The tank 67 issupplied with a liquid inlet 68 and a liquid outlet 69, and also a gasinlet '70 and a gas outlet 71 near the top of the tank. Each of thesensing elements 10 and 10 is placed at a different level, and the gasor liquid content of a sensing element at the particular level at whichit is located is an indication of the liquid level in the tank 67. Theindications by the sensing elements 10 and 10 may be used to operatevalves to control the supply to the tank, or the indications merely maybe used to signal for manual control, or the like.

It is also useful to indicate and control liquid levels in tanks, tomeasure the viscosity of fluids, to indicate and measure gas pressurechanges, or it could be used to only signal with a light or a bell, orthe like, the presence of a gas or liquid in a system rather thanoperate a valving means.

While only one embodiment of our invention has been shown and describedalong with two specific applications of its use, it is our desire thatthe invention shall not be limited to such embodiment, but it is to belimited only in accordance with the scope of the appended claims sincepersons skilled in the art may devise other embodiments still within thelimitations of said claims.

We claim:

1. A gas liquid detector comprising a chamber serving as a vapor trapand adapted to be filled with a liquid, a vibratory reed formed frommagnetic material and having oppositely disposed surfaces, said reedmounted in said chamber for vibration only in directions trans verse tosaid surfaces whereby vibration is substantially prevented by theresistance of liquid in said chamber contacting at least a part of saidsurfaces of said reed, an electromagnetic driving coil external to saidchamber, means causing said electromagnetic driving coil to generate avibratory magnetic field, said electromagnetic driving coil positionedso the vibratory magnetic field is magnetically coupled to said reed andexerts a vibratory force on said reed inside said chamber causing saidreed to vibrate at a useful amplitude only when gas in the liquid entersthe chamber and forces the liquid in said chamber substantially out ofcontact with said reed, an electromagnetic pickup coil external to saidchamber, said pickup coil being magnetically coupled to said reed by themagnetic field generated from said electromagnetic driving coil, and themagnetic field generated from said electromagnetic driving coil formingthe only coupling between said reed and the respective driving coil andpickup coil so that the vibration of said reed induces voltages in saidpickup coil whereby an indication of the presence of gas in the liquidmay be obtained.

2. The gas liquid detector described in claim 1 wherein said reed ismounted in said chamber at one end to permit it to vibrate at anydesired frequency.

3. A gas liquid detector comprising a fluid chamber of substantiallynon-magnetic material, an inlet to said chamber and an outlet from saidchamber, a flat strip of resilient magnetic material having oppositelydisposed surfaces and mounted at one end in the chamber for vibratorymovement in directions transverse to the said surfaces, anelectromagnetic driving coil outside the chamber, means connected tosaid driving coil and causing it to generate a vibratory magnetic field,said driving coil positioned so its axis is substantially parallel tothe direction of vibration of said strip and so its magnetic field iscoupled to the strip whereby it exerts vibratory forces thereon andcauses said strip to vibrate at a useful amplitude only when gas in theliquid enters the chamber and forces the liquid in said chambersubstantially out of contact with said strip, an electromagnetic pickupcoil outside the chamber and on the opposite side of said strip, saidpickup coil being disposed so its axis is substantially parallel to thedirection of vibration of the strip and being magnetically coupledthereto by the magnetic field generated from said electromagneticdriving coil, and the magnetic field generated from said electromagneticdriving coil forming the only coupling between said strip and therespective driving coil and pickup coil so that the vibration of saidstrip induces voltages in said pickup coil whereby an indication of thepresence of gas in the liquid may be obtained.

4. A detector for indicating a change in condition of a fluent materialcomprising a substantially non-magnetic case providing a chamber havingfirst and second end portions joined together by a connecting chamberportion of reduced size extending therebetween, a vibratory reed formedfrom magnetic material and having oppositely disposed surfaces, saidreed being secured at one end to said case and extending from said firstend portion of the chamber through the connecting chamber portion ofreduced size and into said second end portion of the chamber where itterminates in a free end, said reed being mounted in said chamber forvibration only in directions transverse to said surfaces wherebyvibration is substantially prevented by the resistance of liquid in saidchamber contacting at least a part of said surfaces of said reed, anelectromagnetic driving coil disposed externally of said chamber andpositioned on said case at one side of the connecting chamber portion soas to be opposed to one surface of said reed in close proximity thereto,means causing said electromagnetic driving coil to generate a vibratorymagnetic field for exerting a vibratory force on said reed inside saidchamber causing said reed to vibrate at a useful amplitude only when gasin the liquid enters the chamber and forces the liquid in said chambersubstantially out of contact with said reed, and an electromagneticpickup coil disposed externally of said chamber and positioned on saidcase at the other side of the connecting chamber portion so as to beopposed to the other surface of said reed in close proximity thereto sothat the vibration of said reed induces voltages in said pickup coilwhereby an indication of the presence of gas in the liquid may beobtained.

5. A detector for indicating a change in condition of a fluent materialas set forth in claim 4, wherein each of said electromagnetic drivingcoil and said pickup coil has a core of laminated plates of magneticmaterial, and spools of insulation material having cylindrical barrelsrespectively interposed between the core and coil of each of saiddriving coil and said pickup coil.

References Cited by the Examiner UNITED STATES PATENTS 2,550,052 4/1951Fay 73-59 2,616,443 11/1952 Bram 340-237 X 2,633,016 3/1953 Millington73-59 2,696,735 12/1954 Woodward 73-59 2,973,639 3/1961 Banks 73-290 XLOUIS R. PRINCE, Primary Examiner.

CHARLES A. CUTTING, ROBERT L. EVANS, JO-

SEPH P. STRIZAK, RICHARD C. QUEISSER,

Examiners.

1. A GAS LIQUID DETECTOR COMPRISING A CHAMBER SERVING AS A VAPOR TRAPAND ADAPTED TO BE FILLED WITH A LIQUID, A VIBRATORY REED FORMED FROMMAGNETIC MATERIAL AND HAVING OPPOSITELY DISPOSED SURFACES, SAID REEDMOUNTED IN SAID CHAMBER FOR VIBRATION ONLY IN DIRECTONS TRANSVERSE TOSAID SURFACES WHEREBY VIBRATION IS SUBSTANTIALLY PREVENTED BY THERESISTANCE OF LIQUID IN SAID CHAMBER CONTACTING AT LEAST A PART OF SAIDSURFACES OF SAID REED, AN ELECTROMAGNETIC DRIVING COIL EXTERNAL TO SAIDCHAMBER, MEANS CAUSING SAID ELECTROMAGNETIC DRIVING COIL TO GENERATE AVIBRATORY MAGNETIC FIELD, SAID ELECTROMAGNETIC DRIVING COIL POSITIONEDSO THE VIBRATORY MAGNETIC FIELD IS MAGNETICALLY COUPLED TO SAID REED ANDEXERTS A VIBRATORY FORCE ON SAID REED INSIDE SAID CHAMBER CAUSING SAIDREED TO A VIBRATE AT A USEFUL AMPLITUDE ONLY WHEN GAS IN THE LIQUIDENTERS THE CHAMBER AND FORCES THE LIQUID IN SAID CHAMBER SUBSTANTIALLYOUT OF CONTACT WITH SAID REED, AN ELECTROMAGNETIC PICKUP COIL EXTERNALTO SAID CHAMBER, SAID PICKUP COIL BEING MAGNETICALLY COUPLED TO SAIDREED BY THE MAGNETIC FIELD GENERATED FROM SAID ELECTROMAGNETIC DRIVINGCOIL, AND THE MAGNETIC FIELD GENERATED FROM SAID ELECTROMAGNETIC DRIVINGCOIL FORMING THE ONLY COUPLING BETWEEN SAID REED AND THE RESPECTIVEDRIVING COIL AND PICKUP COIL SO THAT THE VIBRATION OF SAID REED INDUCESVOLTAGES IN SAID PICKUP COIL WHEREBY AN INDICTION OF THE PRESENCE OF GASIN THE LIQUID MAY BE OBTAINED.